Program 1: Integrated Building Systems
This project aims to produce a data set underpinning the merit of concentrated solar thermal systems and absorption HVAC systems for integration with buildings. It will reduce operational and financial uncertainties associated with solar thermal heating and cooling in Australia, enabling greater utilisation of this technology.
This project will help develop tools and demonstrate how solar absorption cooling technology can be incorporated into a low carbon building design. It will also provide additional real-world performance data for these systems to be used by industry and building owners to make decisions on solar products. Additionally, experiments will be conducted at CSIRO to determine the feasibility of next generation solar absorption cooling systems.
Program
Project leader
Prof Stephen Foster, UNSW
Project status
Complete
Project period
05/2019 to 06/2019
- Publications
- Posters
- Partners
Peer Reviewed Research Publications
RP1002: Journal Article: Control strategies of domestic electrical storage for reducing electricity peak demand and life cycle cost
Electricity grid capacity is often oversized to ensure it accommodates maximum anticipated peak demand. In South Australia, 25% of the grid capacity is required for less than 1% of the time. To reflect the cost of peak demand in electricity tariffs, demand tariffs consider not only electrical energy consumption (kWh), but also electrical power demand (kW) during a peak period which is from 16:00–21:00 in South Australia. Demand tariffs increase electricity costs for users needing intermittent electrical energy supply with large electrical peak power demand. To reduce the peak demand and the subsequent electricity cost, batteries are being included in the energy system.
In this paper, four control strategies are developed for charging and discharging a battery, and to export and import electricity from the grid. The strategies are simulated with and without a photovoltaic (PV) system using real-time monitored electricity consumption and gross PV generated electricity of a monitored energy-efficient house. The results show that using PV with electrical storage and proper control strategies can reduce both the electricity peak demand and life cycle cost. These results are timely given the recent emergence of small-scale storage technologies and the prediction that these technologies may become commonplace in the near future.
RP1002: Journal Article: Transient simulation and parametric study of solar-assisted heating and cooling absorption systems: an energetic, economic and environmental (3E) assessment
This paper presents energetic, economic, and environmental (3E) analyses of four configurations of solar heating and cooling (SHC) systems based on coupling evacuated tube collectors with a single-effect LiBr–H2O absorption chiller. In the first configuration (SHC1), a gas-fired heater is used as the back-up system, while a mechanical compression chiller is employed as the auxiliary cooling system in the second configuration (SHC2).
The capacity of the absorption chiller is designed based on the maximum building cooling load in these configurations. The third and fourth configurations (SHC3 and SHC4) are similar to SHC2, but the absorption chiller size is reduced to 50% and 20%, respectively. The results show that the highest primary energy saving is achieved by SHC2, leading to a solar fraction of 71.8% and saving 54.51% primary energy as compared to a reference conventional HVAC system. The economic performance of all configurations is still unsatisfactory (without subsidies) due to their high capital costs. However, if a government subsidy of 50% is considered, the results suggest that SHC4 can be economically feasible, achieving a payback period of 4.1 years, net present value of 568,700 AUD and solar fraction of 43%, contributing to 27.16% decrease in the plant primary energy consumption.
RP1002: Journal Article: Thermal-economic-environmental analysis and multi-objective optimization of an ice thermal energy storage system for gas turbine cycle inlet air cooling
In this study, a mathematical model of an ice thermal energy storage (ITES) system for gas turbine cycle inlet air cooling is developed and thermal, economic, and environmental (emissions cost) analyses have been applied to the model. While taking into account conflicting thermodynamic and economic objective functions, a multi-objective genetic algorithm is employed to obtain the optimal design parameters of the plant.
Exergetic efficiency is chosen as the thermodynamic objective while the total cost rate of the system including the capital and operational costs of the plant and the social cost of emissions, is considered as the economic objective. Performing the optimization procedure, a set of optimal solutions, called a Pareto front, is obtained. The final optimal design point is determined using TOPSIS decision-making method. This optimum solution results in the exergetic efficiency of 34.06% and the total cost of 28.7 million US$ y−1. Furthermore, the results demonstrate that inlet air cooling using an ITES system leads to 11.63% and 3.59% improvement in the output power and exergetic efficiency of the plant, respectively. The extra cost associated with using the ITES system is paid back in 4.72 years with the income received from selling the augmented pow
RP1002: Journal Article: A comprehensive, multi-objective optimization of solar-powered absorption chiller systems for air-conditioning applications
Solar heating and cooling (SHC) systems are currently under rapid development and deployment due to their potential to reduce the use of fossil fuel resources and to alleviate greenhouse gas emissions in the building sector – a sector which is responsible for ∼40% of the world energy use. Absorption chiller technology (traditionally powered by natural gas in large buildings), can easily be retrofitted to run on solar energy. However, numerous non-intuitive design choices must be analyzed to achieve the best techno-economic performance of these systems.
To date, there has been little research into the optimal configurations among the long list of potential solar-driven absorption chiller systems. To address this lack of knowledge, this paper presents a systematic simulation-based, multi-objective optimization of three common, commercially available lithium bromide-water absorption chillers – single-effect, double-effect and triple-effect – powered by evacuated tube collectors (ETCs), evacuated flat plate collectors (EFPCs), and concentrating parabolic trough collectors (PTCs), respectively.
To the best of the authors’ knowledge, this is the first study of its kind that compares the optimised designs of the most promising configurations of solar-assisted absorption chillers against a common set of energy, economic, and environmental metrics from a holistic perspective.
A simulation model of these three configurations is developed using TRNSYS 17. A combined energy, economic, and environmental analysis of the modeled systems is conducted to calculate the primary energy use as well as the levelized total annual cost of each plant, which are considered as two conflicting objective functions. By coupling TRNSYS and MATLAB, a multi-objective optimization model is formulated using a genetic algorithm to simultaneously minimize these objectives, thereby determining a set of optimal Pareto solutions corresponding to each SHC configuration. The performance of the proposed systems at their optimal designs is then compared to that of a reference conventional system. A sensitivity analysis is also performed to assess the influence of fuel cost, capital cost of innovative components, and the annual interest rate on the Pareto front of optimal solutions. Overall, the optimization results reveal that of the proposed configurations, the SHC double-effect chiller has the best trade-off between the energetic, economic and environmental performance of the system, having a total cost of ∼0.7–0.9 M$ per year and reducing the annual primary energy use and CO2 emissions by 44.5–53.8% and 49.1–58.2% respectively (relative to the reference conventional system). With the high capital cost associated with these systems, government subsidies and incentives are still required in order for them to achieve satisfactory payback times and become cost-competitive with conventional HVAC systems.
RP1002: Journal Article: A systematic parametric study and feasibility assessment of solar-assisted single-effect, double-effect, and triple-effect absorption chillers for heating and cooling applications
The present work investigates the feasibility of solar heating and cooling (SHC) absorption systems based on combining three types of LiBr–H2O absorption chillers (single-, double-, and triple-effect) with common solar thermal collectors available on the market. A single-effect chiller is coupled with evacuated tube collectors (ETCs) – SHC1. A double-effect chiller is integrated with parabolic trough collectors (PTCs), linear Fresnel micro-concentrating collectors (MCTs) and evacuated flat plate collectors (EFPCs) respectively – SHC2, SHC3, and SHC4. PTCs are employed to provide high-temperature heat to a triple-effect absorption chiller (SHC5). Although triple-effect chillers have been around for a while, this paper represents the first system-level analysis of these chillers coupled with high-temperature solar concentrating collectors for air-conditioning applications.
A simulation model for each configuration is developed in a transient system simulation environment (TRNSYS 17). Furthermore, a unique, comprehensive perspective is given by investigating the impact of characteristic solar beam radiation to global radiation ratios on the techno-economic performance of the proposed SHC plants for a wide variety of climatic regions worldwide. The results of parametric study suggest that a storage volume of around 70 L/m2 is a good choice for SHC1, while 40–50 L/m2 storage capacity is sufficient for the other configurations (SHC2 to SHC5). The simulation results reveal that when the fraction of direct normal irradiance (DNI) is less than 50%, SHC2, SHC3, and SHC5 require larger collector area compared to SHC1, showing there is no advantage in using concentrating collector powered multi-effect chillers over solar single-effect chillers in climates with low DNI level. However, in climates with DNI fractions above 60%, the smallest solar field is achieved by SHC5, followed by SHC2. SHC4, which benefits from both relatively high COP of double-effect chiller and the diffuse component in the solar field, results in the most reasonable trade-off between energetic and economic performance of the system in a wide range of climatic conditions.
RP1002: Journal Article: Exergetic, economic and environmental analyses and multi-objective optimization of an SOFC-gas turbine hybrid cycle coupled with an MSF desalination system
The present study presents thermodynamic, economic and environmental (emissions cost) modeling of a solid oxide fuel cell–gas turbine (SOFC–GT) hybrid system integrated with a multi stage flash (MSF) desalination unit. A heuristic optimization method, namely, multi-objective genetic algorithm (MOGA) is employed afterwards to obtain the optimal design parameters of the plant.
The exergetic efficiency and the total cost rate of the system are considered as the objective functions of the optimization procedure; where, the total cost rate of the system (including the cost rate of environmental impact) is minimized while the exergetic efficiency is maximized. Applying the optimization method, a set of optimal solutions is achieved and the final selected optimal design leads to an exergetic efficiency of 46.7%, and a total cost of 3.76 million USD/year. The payback time of the selected design is also determined to be about 9 years. Although the determined value for the payback period seems to be relatively high for the proposed plant (due to the high capital cost of the SOFC system), this integrated technology is expected to be promising in the near future as the capital costs of SOFCs are decreasing and their operational lifetimes are increasing.
RP1002: Journal Article: Solar-assisted absorption air-conditioning systems in buildings: Control strategies and operational modes
Solar-assisted cooling technology has enormous potential for air-conditioning applications since both solar energy supply and cooling energy demand are well correlated. Unfortunately, market uptake of solar cooling technologies has been slow due to the high capital cost and limited design/operational experience. In the present work, different designs and operational modes for solar heating and cooling (SHC) absorption chiller systems are investigated and compared in order to identify the preferred design strategies for these systems.
Three control scenarios are proposed for the solar collector loop. The first uses a constant flow pump, while the second and third control schemes employ a variable speed pump, where the solar collector (SC) set-point temperature could be either fixed or adjusted to the required demand. Series and parallel arrangements, between the auxiliary heater and the storage tank, have been examined in detail from an energy efficiency perspective. A simulation model for different system layouts is developed in the transient system simulation environment (TRNSYS, Version 17). Simulation results revealed that the total solar fraction of the plant is increased by up to 11% when a variable speed solar loop pump is used to achieve a collector set-point temperature adjusted according to the building load demand. Another significant finding of this study is that a parallel configuration for the auxiliary heater out-performs a conventional series configuration. The yearly performance of an auxiliary heater in parallel with the storage tank enhances the plant solar fraction, and the average collector efficiency, by up to 13% and 9%, respectively (as compared to the same components in series). Taken together, nearly 20% higher solar fraction (as compared to conventional designs) is possible through the control strategies and operational modes presented here without adding a substantial capital cost to the system.
RP1002: Journal Article: Multi-Objective Optimisation of a Solar-Powered Triple-Effect Absorption Chiller for Air-Conditioning Applications
In this paper, a detailed simulation model of a solarpowered triple-effect LiBr–H2O absorption chiller is developed to supply both cooling and heating demand of a large-scale building, aiming to reduce the fossil fuel consumption and greenhouse gas emissions in building sector.
TRNSYS 17 is used to simulate the performance of the system over a typical year. A combined energeticeconomic-environmental analysis is conducted to determine the system annual primary energy consumption and the total cost, which are considered as two conflicting objectives. A multi-objective optimization of the system is performed using a genetic algorithm to minimize these objectives simultaneously. The optimization results show that the final optimal design of the proposed plant has a solar fraction of 72% and leads to an annual primary energy saving of 0.69 GWh and annual CO2 emissions reduction of ~166 tonnes, as compared to a conventional HVAC system. The economics of this design, however, is not appealing without public funding, which is often the case for many renewable energy systems. The results show that a good funding policy is required in order for these technologies to achieve satisfactory payback periods within the lifetime of the plant.
RP1002: Conference Paper: Simulation of Rooftop Photovoltaic Shading using TRNSYS
The shade effect of a rooftop photovoltaic (PV) collector on a roof is usually ignored in building energy simulation in Transient System Simulation (TRNSYS) software. This disregard is due to either the unavailability of a suitable shading component in the simulation software or to an assumption that the shade on opaque surfaces, such as roofs, has small impact on the indoor temperature and the subsequent heating and cooling energy usage. However, for a relatively large collector area, ignoring the collector shadow on the roof may produce inaccurate results.
In this paper, a novel component is developed in MATLAB to simulate the shade effect of a collector using TRNSYS. This is a conference paper from the 3rd International Renewable and Sustainable Energy Conference in Morocco, 2016.
RP1002: Journal Article: Solar-powered absorption chillers: A comprehensive and critical review
To read the publication printed in Energy Conservation and Management, Volume 171, 1 September 2018, pages 59-81.
RP1002: Conference Paper: Multi-effect absorption chillers powered by the sun: reality or reverie
SHC 2015, International Conference on Solar Heating and Cooling for Buildings and Industry - published in Science Direct.
CRCLCL project reports
RP1002: Conference Paper: Solar-powered absorption chillers for air-conditioning applications: simulation and techno-economic evaluation
Presentation by Ali Sharazi at the AIRAH Solar Cooling workshop in Brisbane, 2014.
RP1002: Project Report: Concentrated Solar Thermal Systems and Absorption HVAC Systems
The project aimed to explore the feasibility of using solar thermal collectors to drive single, double, and triple effect absorption chillers. While it was originally scheduled to include experiments and a demonstration system with a commercial partner, the partner stopped trading in Australia before the project commenced. Thus, the project became much smaller, with a budget only for a PhD top-up scholarship. Despite this, a lot of new knowledge was gained through the insights of the PhD student, Ali Shirazi, who has now gone on to work a postdoctoral researcher at the Australian National University. Thus, although the project had limited commercial outputs, it did produce ~10 peer-reviewed publications.
Student poster 2015: RP1002 Concentrated solar thermal systems and absorption Hvac systems
Student poster - Participants Annual Forum 2015 - Ali Shirazi
Solar absorption systems for air-conditioning applications in large-scale buildings in Australia
Research Snapshot Poster - RP1002
Research Snapshot A3 size poster from Participants Annual Forum 2014
Student Poster 2014 - RP1002
Student Poster - Participants Annual Forum 2014, Ali Shirazi - Size A2.